Oscillator control system for electric bonding machines



H. B. FUGE OSCILLATOR CONTROL SYSTEM FOR Nov. 8, 1949 ELECTRIC BONDINGMACHINES Filed NOV. 23, 1946 OSL'ILLATOR INVENTOR. y 5. Page Haw r BY W1TNESS WA) L-MF2MZ; MA

ATTORJVEY Patented Nov. 8, 1949 OSCILLATOR CONTROL SYSTEM FOR ELECTRICBONDING MACHINES Harry B. Fuge, Somerville, N. J assignor to The SingerManufacturing Company,

Elizabeth,

N. J a corporation of New Jersey Application November 23, 1946, SerialNo. 711,989

3 Claims. 1

This invention relates to a control system and particularly to a systemfor controlling the turning on and off of an electron tube oscillatorresponsively to the speed of a feed drive for advancing material througha radio-frequency electric field supplied by said oscillator.

It is customary and desirable, with bonding machines in which thematerial to be bonded is progressively fed through an electric fieldsupplied by an oscillator, to provide means for rendering the oscillatorinefiective whenever the feed stops and to render it effective when thefeed starts. Formally, this has been accomplished by a switch operatedfrom the foot-treadle which operates to clutch and de-clutch the machineshaft from the machine driving motor. Certain disadvantages are inherentin this treadle switch arrangement, among which the following are themore important:

1. The difficulty of determining a single mechanical settin for thetripping point of the switch relative to the treadle position forminimum feed of unbonded material during both the starting and thestopping periods.

2. The necessity of frequent readjustment of this setting due tocompensation for the wear of clutch and brake surfaces.

It is a primary object of this invention, therefore, to provide anon-oif control for an oscillator of an electric bonding machine whichcontrol shall have an electrical setting for timing with respect to feedwhich setting remains independent of the ordinarily adverse effects ofsurface wear of the clutch and brake employed to control the feed drive.

This object is attained, according to the invention, through the use ofa control system which responds, with minimum time lag, directly to thespeed of the feed.

The invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawing and itsscope will be pointed out in the appended claims.

Referring to the drawing, the single figure is a diagrammaticillustration of a control system wherein the invention has beenembodied.

The figure shows an oscillator I, preferably of the type employingelectron tubes requiring direct-current voltage for the plates thereof.A power rectifier 2 is connected to the oscillator l by means of leads 3and 4 and receives its energy from the single-phase, alternating-currentsupply S by way of leads 5 and 6 through the contacts of relay 1. Theradio-frequency output of the oscillator l is connected to electrodes 8and 9 v 2 by means of coaxial cable I0. Material I I, to be bonded, isfed through the electric field set up between the electrodes 8 and 9.This feed is effected in a direction indicated by the arrow 35 by meansof a feed wheel l2 cooperating with a roller presser l3 which may alsobe a driven feed wheel. The feed Wheel 12 is priven from acontinuously-running motor l4 through a clutch and brake transmitter isrendered selectively effective for starting and stopping the feed uponactuation of a foot treadle 16. This transmitter l5 may be of the typeshown and described in the U. S. Patent No. 1,652,319 to which referencemay be had for a more complete description thereof.

A rotation generator I! of the inductor alternator type, shown anddescribed in the copending application Serial No. 646,972 of James W.Momberg filed February 12, 1946, now U. S. Patent No. 2,462,761, ismechanically connected to the output shaft of the transmitter I5 so thatits speed will be proportional to that of the feed wheel. This generatorll generates an alternating voltage which is proportional to its speedand therefore to the feed wheel speed and thus to the average linearfeeding rate. Connected electrically to the generator I! by means ofleads I 8 and I9 is a potentiometer 20 with an adjustable slider 2| fortaking off any desired proportion of the total voltage generated. Thisproportional voltage is applied through a current-limiting resistor 22to a control or starter electrode 23 and cathode '24 of a cold-cathodegas triode 25 having an anode 26. This tube may be a standard commercialR. C. A. OA l-G tube. The cathode 24 is connected in series with thecoil 21 of a relay 28 to one side of the supply S. The other side of thesupply S is connected to the anode 26 so that conduction through thetube 25 from cathode to anode will cause current to fiow in the coil 21of relay 28. Due to rectification within the tube, the coil current willbe pulsating D.-C. and, in order to filter out the A.-C. componentthereof, a series R. C. filter comprising resistor 29 and capacitor 30is connected across the coil 21.

The relay 28 operates to connect coil 3| of relay 1 across the supply Sby way of leads 32, 33 and 34. It will be understood that relays l and28 are shown in their normally-open unexcited condition and, when theirrespective coils are excited, they pick up to close their contacts.

Tube 25 has special and well-known characteristics so that, for a givenvoltage impressed across the anode 26 and cathode 24, there is a certainminimum voltage above which, if impressed across the starting electrode23 and the cathode 24, will cause current conduction through the tubefrom cathode to anode.

In operation, when the foot-trcadle i6 is actuated, the motor M isconnected to drive the fee wheel l2 through the clutch and braketransmission l5, and material ll begins to move through the fieldbetween electrodes 3 and 9;. Simultaneously, generator l'l is beingdriven up to speed with the feed wheel is and is generating a voltageproportional to its speed at any instant. Thus, as the feed accelerates,the voltage increases accordingly and a predetermined proportion of saidvoltage, controlled by the position of the slider 2i is impressed on thestarting electrode 23 and cathode 24 circuit of tube When this voltagehas increased to a value determined by the voltage from S impressed onelectrodes 2% and 2%, the tube 25 will conduct and current will fiowfrom the supply S through coil 2'2", and relay 28 will pick up andconnect relay coil across the supply S. This will cause relay '3 to pickup and connect the power rectifier to the supply S, whereupon theoscillator plates are supplied with D.-C. voltage and radio-frequencyenergy is liberated'in the material it between electrodes 8 and 9.

' It is clear that there will be a time delay rep resented by the timetaken for the feed to accelcrate to a speed productive of SllfilClBZltvoltage to cause tube 25 to conduct and turn on power to the oscillator.During this delay period, there may be feed without bonding and itshould, therefore, ordinarily be kept to a minimum. Due to the very highacceleration with the clutch-type transmitters usually employed, thisdelay time will be very small and, with the control tied directly to thefeeding rate, very little material need be fed before bonding begins.

Similarly, when stopping the machine, the treadle is released to brakethe feed drive, the feed rate decreases and the voltage from alternatorl'l falls oii quickly to a value below that necessary to cause tube 25to conduct, whereupon rela s 23 and l drop out and remove direct-currentpower from the oscillator. Very shortly thereafter, the feed stops and,if material is being fed during this period, it will not be bonded.

Thus, it is perceived that I have provided an oscillator control systemwhich is independent of treadle position and which respondsautomatically to the feeding rate. Since the response of such a systemis independent of how the feeding rate is obtained, it is clear thatwear of transmission elements, such as clutch and brake shoes. can haveno efiect on chan ing the control setting.

It is evident that, by manual adjustment of the slider ii, the motorspeed at which tube 25 conducts and relay 2% picks up may be preset andthereafter said setting does not change, regardless of wear of theclutch and brake elements of the transmitter 55.

Although there is shown herein, as a preferred form, an embodiment inwhich the electrodes 8 and 9 are elements separate from the feedingelements 52 and it, the invention is not to be considered as so limitedbut includes within its scope that form in which the feeding elements 12and i3 are also the electrodes in which case the connections from theend of the coaxial cable are made to said feeding elements.

It is to be understood that various changes may be made in theconstruction, arrangement and interrelation of the parts constitutingthe invention without departing from the spirit thereof.

Having thus set forth the'nature of the invention, what I claim hereinis:

l. A control system for an electric bonding machine, comprisin aradio-frequency oscillator, iectrodes electrically connected to saidoscillater to set up an electric field, feeding-means for advancingmaterial through said field, a rotatable shaft for actuating saidfeeding-means, a pilot generator connected for rotation with said shaftand producing an output voltage of magnitude proportional to the speedof said shaft, electronic means electrically connected to said pilotgenerator, and relay means connected to said electronic means andoperative responsively to said shaft speed to turn on and off theoscillator in step with the respective starting and the stopping of thefeed. i

2. A control system for an electric bonding machine comprising aradio-frequency oscillator, electrodes connected to said oscillator forestablishing an electric field therebetween, feeding-means for advancingmaterial through said field, a generator connected for rotation uponactuation of said feeding means and effective to produce an outputvoltage of magnitude proportional to its speed, means for selecting apredetermined portion of said voltage, electronic means connected toreceive said selected proportional voltage, and relay means connected tosaid electronic means and operative responsively to the rate of advanceof the material by said feeding means whereby to turn on and oil-theoscillator in step with the respective starting and stopping of saidfeeding means.

3. in an electric bonding system, a radioirequency oscillator,electrodes connected to said oscillator for establishing an electricfield, a power rectifier connected to supply power to said oscillator,feeding means for advancing material to be bonded through said field,generator means connected for rotation upon actuation of said feedingmeans and effective to produce an output voltage proportional to itsspeed, electronic means connected to receive said voltage, and relaymeans connected electrically to said electronic means and operativeresponsively to the rate of advance of the material by said feedingmeans to render said power rectifier ineffective to supply power to saidoscillator.

HARRY B. FUGE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,967,198 Caputo July 17, 19342,325,401 Hurlston July 2'7, 1943 2,391,086 Crandell Dec. 18, 19452,419,214 Holman et a1. Apr. 22, 19 i? I 2,425,123 Quayle et a1. Aug. 5,194;?

